1. Field of the Invention
The invention relates to a data transmission system using an optical fiber. More particularly, the data transmission system can be applied for HDCP (high-bandwidth digital content protection) applications through fewer parallel optical fibers.
2. Description of the Prior Art
HDCP is a digital rights management specification developed by Intel Corporation to protect digital entertainment traveled across DVI (digital visual interface) or HDMI (high definition multimedia interface) connections from being illegally copied. The HDCP specification provides a robust, cost-effective and transparent method for transmitting and receiving digital entertainment content through DVI/HDMI-compliant digital displays (e.g., high definition television or flat panel such as plasma, LCD and/or DLP, etc).
In general, HDCP encrypts the transmission of digital content between the video source and the digital display. And, HDCP is not designed for preventing the digital content from being copied or recorded per se, but rather designed for protecting the integrity of content during transmission. The video source or transmitter could be, for instance, a DVD player, a computer, or a set-up box. The digital display or receiver could be, for instance, a digital television, a monitor, or a projector. The implementation of HDCP requires an HDCP-enabled device which has a set of secret keys. During authentication, the receiving device will only accept content after it acknowledges the keys. To further protect the digital content, the transmitter and receiver generate a shared secret key value that is continuously checked throughout the transmission. After an authentication is established, the transmitter encrypts the data and sends it to the receiver for decryption.
High-bandwidth transmission of digital content is usually achieved by one of two means: shielded copper wires (such as coaxial cable) or fiber optic cable. The first generation of HDCP transmission systems was known of using parallel-shielded copper wire cables, such as DVI cables or HDMI cables. However, the bandwidth of this kind of cable has limitations in transmitting data. When the distance of transmission is elongated, the cost of the shielded copper wire cable will increase and the transmitted data will decay rapidly. In view of this fact, a multiple parallel optical fiber link was introduced between transmitters and receivers. Nevertheless, the multiple parallel optical fiber link traditionally employs multiple optical fibers for the HDCP applications.
For example, the traditional optical-fiber-based HDCP transmission system transmits TMDS (time minimized differential signal) from the video source or the transmitter to the digital displays through four optical fibers, and transmits data in the HDCP format through two optical fibers. However, for longer distance applications under the configurations, the cost of multiple parallel optical fibers is concerned, and the arrangement and maintenance of the multiple parallel optical fibers most certainly increase the loading.